Many chemical analysis applications, such as gas and liquid chromatography, rely on the flow of fluid through one or more tubes and couplings. For example, in gas chromatography, one or more tubes, referred to as columns, are used to analyze a sample of material to determine its components. A chromatographic column can be, for example, a packed column or a capillary column. As the material under analysis flows through the column, the interaction of the material under analysis and the material on the inside of the column results in the constituent components of the material under analysis eluting from the column at different times. This elutant from the column is transferred to a detector. Detector response is indicative of the amount of elutant passing through the detector. In the case of mass spectrometer detectors, the detector can also provide information to help identify the elutant.
During gas chromatography, it is sometimes desirable to cause a gas to flow through the column in a direction opposite the normal direction of flow used during analysis. This is referred to as “backflushing” the column. There are many circumstances in which it is desirable to backflush a chromatographic column. For example, it is desirable to backflush a chromatographic column when analyzing compounds that include highly-retained components that may not elute from the column, thereby contaminating the column and negatively affecting subsequent analyses.
Common backflush techniques rely on the use of additional system components such as pressure control devices, gas supply lines, connection devices, additional columns acting as restrictors, and additional fluid flow components.
FIG. 1 is a schematic diagram illustrating an arrangement for column backflush in an existing gas chromatograph system. The gas chromatograph system 10 includes an inlet pneumatic module 12 coupled to a chromatographic inlet 14. The entrance of the column 16 is connected to the chromatographic inlet 14. A sample (not shown) to be analyzed can be introduced to the column through the chromatographic inlet 14 over connection 13. A gas, which can be referred to as a carrier gas, flows from the inlet pneumatic module 12 through the chromatographic inlet 14 to the column 16. The inlet pneumatic module 12 controls the pressure and flow of the carrier gas to the chromatographic inlet 14 and the column 16, and controls the pressure at the entrance of the column 16. The exit of the column 16 is connected to an intermediate connection device, which, in this example, is illustrated as a purged union 18. The purged union 18 facilitates the connection of the column 16 to an external restriction 24. An auxiliary pneumatic module 22 controls the exit pressure of the column 16, and the flow through the purged union 18. The external restriction 24 is coupled to a detector 26. A detector pneumatic module 28 controls the pneumatic functions of the detector 26.
Although not present during normal chromatographic analysis, the purged union 18, the auxiliary pneumatic module 22 and the external restriction 24 are required so that a backflush flow can be established in the column 16. For normal chromatographic analysis, the exit of the column 16 is directly connected to the detector 26 with no restrictor, no additional pneumatic module, and no purged restrictor. In addition, the process of configuring the system 10 for backflush can take considerable time, requires additional operator training and/or expertise and can represent a significant change in operational procedures.
Therefore, it would be desirable to have the ability to backflush a chromatographic column with minimum additional hardware, expertise, and change to standard operating procedures and practices.